Titration apparatus



Patented Dec. 22, 1942 UNiTED TITRATION APPARATUS Alexander I. Newman,Chicago, Ill., assignor to Precision Scientific Company, Chicago, 111.,a corporation of Illinois Application June 24, 1940, Serial No. 342,039

2 Claims.

The invention relates to improvements in titration apparatus.

customarily, titration tests are carried on by draining test liquidsfrom successive burettes into a reaction receptacle and observing bymeans of graduations on the burettes, the quantity of test liquids whichmust be added to a reaction solution in the receptacle in order to bringabout a predetermined reaction. For example, two burettes or graduatedtubes may be loaded respectively with an alkaline solution and an acidsolution while a litmus solution, 1. e., one which changes color upon apredominance of acid or alkali in contact with it, is placed in thereaction receptacle. The liquid is drained from one burette into thelitmus solution until the latter changes color, whereupon the quantityof liquid which had to be added for this purpose is noted. Then thereceptacle is placed under the other burette and liquid is drained fromit into the receptacle until the litmus solution again changes color. Asbefore, the amount of added solution necessary to bring about thereaction is observed.

Precision of results obtained with an apparatus of the characterdescribed above depends direct- 1y upon, first, the accuracy of thereadings of the quantities of liquid withdrawn from the burettes, and,second, upon the accuracy with which the operator notes the precisepoint of visual change in the liquid in the receptacle, denoting thatthe reaction point has been reached. It will be appreciated that thegraduations on the burettes are usually very fine, entailingconsiderable eye strain in reading them precisely, and, further,

that the color changes or the like in the recep- 1 tacle may at first berather pale when the reaction first sets in, again requiring minuteobservation. Accordingly, the general aim of the present invention is topromote the accuracy of the results obtainable in such an apparatus, anda diminution in the strain on the operator, by virtue of theincorporation in the apparatus of a novel illuminating arrangement.

More specifically, it is an object of the invention to provide atitration'apparatus embodying means for sulfusing with bright light theburettes and reaction receptacle, as well as means forming a whitebackground behind them, so that the graduations on the burettes willstand out in sharp relief and color changes in the receptacle contentswill be easily observable, the lighting system being of the indirecttype so that there is no glare directly in the user's eyes.

- Another object is to provide a titration apparatus incorporating anindirect lighting system,

so correlated in a structural sense with the instrumentalities of theapparatus as to afford a compact unit and one which is also rugged inconstruction and low in cost.

Further objects and advantages of the invention will become apparent asthe following description proceeds, taken in connection with theaccompanying drawing in which:

Figure 1 is a general perspective View of a titration apparatusembodying the invention.

Fig. 2 is a transverse sectional view taken subs-tantially along theline 2-2 in Fig. 1.

Fig. 3 is a general perspective view, though on a smaller scale thanFig. 1, of a modified form of titration apparatus also embodying theinvention.

Fig. 4 is an enlarged transverse sectional view taken substantiallyalong the line 4-4 in Fig. 3.

Although but two embodiments of the invention have been illustratedherein it will be apparent to those skilled in the art that variousmodifications and alternative constructions may be made to meetparticular exigencies of use. According- 1y, it is to be understood thatI do not intend to limit the invention by the particular disclosure madebut aim to cover all modifications and al ternative constructionsfalling within the spirit and scope of the invention, as expressed inthe appended claims;

In the first illustrative embodiment of the invention (Figs. 1 and 2)the apparatus shown comprises a pair of burettes or graduated verticaltubes l0 having stop cocks II at their lower ends. Test liquids fromalternate ones of these burettes are drained into a reaction receptacleshown as a transparent glass beaker l2. The burettes themselves are alsomade of transparent glass so that the quantities of liquid withdrawnfrom them from time to time can be determined by reading the successivelevels of the liquid shown by the graduations.

The burettes H] are mounted on a structure which forms, first, a supportfor them, second, a light colored or white background to enhance theease of observation of them, and, third, a refiector for diffusing lightthrough the burettes and the receptacle I2. This structure comprises ahollow disk shaped sheet metal base I4. Rising from the rear of thisbase is a sheet metal reflector shield I5 which is generally channelshaped in cross section, in the present instance, semicircular. Theburettes III are supported from the front face of this shield byreleasable grip type spring clips [6 of well known form, and which arepivoted on the front face of the shield on brackets I! fixed to thelatter.

As a source of illumination a fluorescent tube or tubular gaseousconduction lamp I8 is used. Suitable sockets I9 and receive the upperand lower ends respectively of this lamp. The lower socket 20 is mountedon the base I4 while the upper socket I9 is carried on a bracket 2Ifixed to the shield I5. A suitable reactor 22 for the lamp I8 may bemounted within the hollow base I4 and a plug type connector (not shown)provided for connecting the lamp to a source of current. A tumblerswitch 23 at the front of the base is used to turn the lamp on or off.

The lamp I8 is located centrally in front of the shield I5 and withinits confines as best shown in Fig. 2. Thus the lamp lies on a radiusfrom the center of the base passing through the center of the shield I5.On the other hand, the burettes III are located one on each side of thelamp I8 and somewhat forwardly of it. The

relative location of the lamp and burettes is so chosen that light fromthe lamp will be reflected by the shield I5 on to the burettes, thelatter being disposed close to the focal centers of the illuminatingsystem as shown by the dot-dash lines L in Fig. 2. The burettes are alsoilluminated by light falling directly on them from the lamp I8 as wellas by the reflected light noted. The illumination is, in fact, socomplete with the present apparatus as to afford a very closeapproximation of daylight conditions. In addition, the exact shape ofthe reflector shield is not critical since accurate direction of lightrays cannot be obtained from a fluorescent lamp, anyhow, a generalsuffusion of light over the parts illuminated being obtained.

To prevent light from the lamp I8 glaring in the operator's eyes, anopaque guard strip or screen 24 is positioned in front of the lamp. Thelower end of the strip is fixed to the base I4 while its upper end iscarried by a forwardly projecting bracket 25 on the shield I5. The guardstrip 24 not only effectually intercepts light rays which wouldotherwise pass directly to the observers eyes but also reflects themback to the shield I5 where they are in turn reflected to the burettes,the inside of the strip 24 being desirably white for that purpose.

In order to form a noninterfering background for the burettes I0 andbeaker I2 the inside or front surface of the shield I5, as well as thetop of the base I4, are preferably white. Such a white surface affords agood contrast to the color of the liquids in the burettes as well as tothe color of the reaction solution in the beaker I2. In addition, suchwhite surfaces have a low degree of light absorption, or, in otherwords, constitute good reflecting surfaces for reflecting light from thetube I8 onto the burettes and receptacle.

In the use of the titration apparatus described,

a quantity of acid solution may be placed in one of the burettes II) anda quantity of alkaline solution in the other. The solution being testedis placed in the beaker I2 and the initial quantities of solution inboth the burettes are, of course, noted. This is done with the lamp I8turned on so that the entire interior of the apparatus is suffused withlight and the burettes, as well as the receptacle I2, fully illuminated.The beaker I2 is then placed beneath, say, the right hand burette, asshown, and the stop cock II for this burette opened so that the solutionfrom the burette is slowly drained from the receptacle. Such draining ofthe solution is continued until the operator observes a color change orother desired reaction in the beaker. Thereupon he shuts off the stopcock and observes the amount of liquid withdrawn from the burette, tobring about the reaction, as indicated by the change in level of thesolution in the burette. Then the beaker I2 may be shifted to a pointbeneath the other burette and the operation repeated. This general typeof operation is, of course, familiar, the improvement in operationherein obtained lying in the ease and accuracy with which the readingsof solution level in burettes may be read and the reaction changes inthe beaker noted.

A modified form of titration apparatus also embodying the invention hasbeen shown in Figs. 3 and 4. In this instance a pair of burettes I0,identical with those described above are also provided, as is a beakerI2. To illuminate these instrumentalities, however, two fluorescentlamps I8, rather than one, are now used. In this case the base I I isgenerally like the base I4, previously described, except that it iselliptical rather than circular in shape. This is done in order that ashield I5 rising from it may present a front surface of parabolic,rather than semi-circular cross section, this difference in shape beingdesirable when using two sources of illumination disposed laterally ofthe burettes and at the points indicated in Fig. 4.

One advantage of the modified construction shown in Figs. 3 and 4, isthat the screening of the lamp, to prevent glare in the operator's eyes,is accomplished simply by bending the front edge portions I5 of theshield Iii inward about the fronts of the lamps I8 rather than providinga separate guard structure for the purpose.

The operation for the apparatusof Figs. 3 and 4 is substantiallyidentical with that heretofore described for Figs. 1 and 2. As before,the burettes I0 and beaker I2 are fully illuminated for precisionobservation, being suffused with light from the indirect lighting sourceso that they can be readily observed and, yet, there will be no glare oflight in the operators eyes. In both instances the apparatus is verycompact, low in cost, and of such form that it can be readily handled asa unit both in merchandising and during its use in the laboratory.

I claim as my invention:

1. In a titration apparatus, the combination of a base, a vertical sheetmetal shield of substantially half round cross section rising from thebase of the rear side thereof, a forward projection at the top of theshield, a fluorescent electric lamp of tubular form supported in uprightposition between said projection and the base with the longitudinal axisof the lamp displaced toward the center of the base from the shield andlying substantially on a radius of the base projecting toward the centerof the shield, means for supporting a pair of burettes one on each sideof the lamp directly in front of the shield and at points close to thefocal points of light falling on the respective halves of the shield,the forward face of the shield and the top of the base beingsubstantially white to form a non-interfering and low light absorptionbackground, and an opaque strip fixed to said base in front of the lampto cut off direct glare from the lamp into the eyes of an observerstationed in front of the apparatus.

2. In a titration apparatus, the combination of a base, a vertical sheetmetal shield of generally curved cross section rising from the base atthe rear side thereof and presenting a concave forward face, afluorescent electric lamp of tubular form supported in upright positionin front of a portion of said shield and above said base, means forsupporting a pair of burettes in upright position in front of saidshield in parallel spaced relation to each other and to said lamp withat least one of said burettes disposed close to a focal point of thelight reflected by said shield from said lamp, the forward face of theshield and the top of the base being substantially White to form anon-interfering and low light absorption background, and an elongatedupright opaque barrier rigid with said shield and positioned in front of5 the lamp to cut off direct glare from said lamp into the eyes of anobserver stationed in front of the apparatus.

ALEXANDER I. NEWMAN.

